Water remains a liquid
over a very wide temperature range, namely, a range of 0°C
to 100?C, between freezing and vaporization. This spans
the temperatures of most parts of the Earth where life can
occur.
Water has a very high
specific heat, which means that it can absorb or lose much
heat before its temperature changes. This is important in
maintaining body heat in mammals, such as ourselves. It
takes a lot of energy to start evaporation because water
has a high latent heat of vaporization. For this reason,
water evaporates slowly from ponds and lakes, where many
life forms are dependent on it.
Water is less dense in
its solid state than in its liquid state, so that ice
floats instead of sinking. This property permits life to
develop in polar regions and subpolar regions where ice
floats and allows life to continue living below the
surface. If ice were heavier than water, it would sink,
and more ice would form on top of it. As a result, all
life in the waters would be trapped in the ice in the many
areas of the world where it gets cold enough to freeze
water.
Water's surface tension (the ability of a substance to
stick to itself) makes it an excellent substance to float
heavy objects upon. Water not only sticks to itself, but
also to other surfaces, and this allows it to move against
gravity, which is very important to plants when
transporting water form the soil to their leaves. This
upward motion is known as capillarity or capillary
movement.
